[theora-dev] Theora streaming

Arc arc at indymedia.org
Thu Feb 27 11:49:31 PST 2003

On Thu, Feb 27, 2003 at 07:40:03PM +0100, Guenter Bartsch wrote:
> hallo arc,
> > The chaining together is actually quite simply, if you have two legal
> > ogg files you simply concat'ate them together.. even the traditional
> > "cat" command can do this legally (correct me if I'm wrong, it works
> > with Vorbis).
> humm - but wouldn't that result in a file in which at some point a new
> vorbis stream with a different serialno starts? how are players supposed
> to handle this - please keep in mind that some ogg files may contain
> more than one audio track so just playing any vorbis packet no matter
> what serialno it has is not a good idea

Ogg supports chaining different bitstreams together, this is apparently
exactly what Icecast2 does.  It plays one stream, receives an EOS (end
of stream), then the next packet is a BOS for the next stream.

In Ogg Theora you have a Theora and Vorbis bitstream - their BOS packets
for each stream are one after another, the EOS for each are one after
another, and at that point the file can either end or a new set of
bistreams can begin.  If you take the next segment to be included and
include it, the BOS's for the Theora and Vorbis will then be next and it
should continue as before.

I've heard that Theora files work fine if you play them through
Icecast2.. the player example for alpha-1 seems to (sometimes) play the
test encodes when it's cat'ed together:

cat >test-double.ogg testlong.ogg testlong.ogg
./player_example test-double.ogg

However with different files it doesnt work, simply says "done" after
playing the first piece.  But of course it's alpha and only an example..
prehaps it only plays through to the second if it's the same serial no,
or prehaps the change of resolution has it mixed up.

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